Changes in objectively measured BMI in children aged 4-11 years: Data from the National Child Measurement Programme

Abstract

Background This study looked at the degree of weight gain between the first (Reception) and last year (Year 6) of primary school and how weight status in Reception predicts becoming overweight/obese by Year 6. Methods A longitudinal sample of 1863 children was created using two time points (2006/7, 2012/13) from the National Child Measurement Programme (NCMP) in South Gloucestershire. T-test and logistic regression were used to test the difference between the BMI z-scores and BMI percentiles, and predict the probability of being overweight (BMI ≥ 85th) or obese (≥95th) at Year 6 based on BMI percentile in Reception. Results Of those children who were obese at Reception age, 68% were obese at Year 6. Compared with children with a BMI in the 2nd to 49th percentile range, children between the 75th and 84th percentiles of BMI at Reception age were 10 times more likely (odds ratio (OR) = 10.18, P < 0.01), and those with a BMI between the 85th and 94th percentiles were 13 times more likely (OR = 13.38, P < 0.01), to become obese by Year 6. Boys were more likely than girls to revert to a healthy weight. Conclusions This is the first study to link data from the NCMP. It provides estimates of prevalence and offers new evidence on obesity emergence and gender differences.